This invention pertains to a position and movement control system for a manipulator device such as a crane or X-Y positioning machine. More particularly, the present invention pertains to controlling and positioning the manipulator device based on measurements and signals obtained from encoding and absolute distance standard such as a coded strip chart or the like having a uniquely different pattern for each increment of position or distance. The present invention is particularly applicable for use in controlling a manipulator crane used for handling fuel and core elements in a nuclear reactor.
Previous manipulator cranes for nuclear reactors and most X-Y manipulating devices operate on a differential or relative movement principle. Such prior art systems involve encoders and incremental counters for sensing and measuring the number of incremental steps or distances of movement from an initially established reference position. At any time the incremental counter reflects the number of incremental units the device has moved from its initial reference position. Reliable operation of the system is thus completely and totally dependent on establishing and maintaining the initial reference position.
If the initial reference position is lost or changed in such prior art systems, the total system must be completely reprogrammed or reorganized. Loss of the initial reference position can and does occur, under such exemplary circumstances as power failures, static noise bursts, service and maintenance to mechanical components of the system and upon first starting a newly installed prior art device.